An ultrafine high-entropy zirconate-silica flexible fiber membrane and its preparation method

Abstract

The present invention discloses an ultrafine high-entropy zirconate-silica flexible fiber membrane and a preparation method thereof, belonging to the field of preparation of new ceramic fiber materials. The chemical formula of the fiber membrane is RE2Zr2O7-SiO2, which is composed of amorphous silica-coated high-entropy rare-earth zirconate nanoparticles and has an RE / Zr-O-Si amorphous interface; the RE is composed of five rare-earth metal elements. The high-entropy zirconate-silica fiber membrane prepared by the present invention has uniform composition, good flexibility, can be bent and folded, has extremely high purity, small and uniform diameter, dense structure, and the grain size of the high-entropy zirconate is within 10 nm at high temperature, and has good anti-sintering performance.

Description

Technical Field

[0001] The present invention relates to an ultrafine high-entropy zirconate-silica flexible fiber membrane and a preparation method thereof, belonging to the field of preparation of new ceramic fiber materials. Background Art

[0002] Zirconia materials have properties such as high temperature resistance, high strength, wear resistance, high melting point, low thermal conductivity, and high thermal expansion coefficient, and are indispensable thermal protection materials in thermal protection systems such as aerospace and modern advanced industries. However, a single zirconia material is extremely prone to phase change in a service environment with alternating hot and cold, and is accompanied by a volume change of 3-7%. It is difficult for zirconia materials to be stably applied in the long term. In addition, the growth rate of single zirconia particles at high temperature is relatively fast, and the coarsening of grains will further reduce its heat insulation performance, which seriously limits the application of zirconia materials in the field of thermal protection. Rare earth zirconate materials have lower thermal conductivity and better corrosion resistance than single zirconia materials. However, rare earth zirconate materials have strong chemical bonds, poor mechanical properties, and low toughness, and it is difficult to fully meet the application requirements of thermal protection materials.

[0003] High-strength ceramic fibers usually have excellent self-supporting properties, and their flexible and rigid products have characteristics such as low density, high porosity, and low thermal conductivity. Preparing rare earth zirconate ceramics into fibers can not only maintain the excellent properties of rare earth zirconates themselves, but may also be expected to further reduce the thermal conductivity of rare earth zirconate materials. However, the growth of grains at high temperature will cause shrinkage deformation, embrittlement and breakage of polycrystalline fibers, resulting in a decrease in their strength and toughness. How to prepare rare earth zirconate ceramic fibers with good anti-sintering performance and maintain high strength and flexibility at high temperature is a very challenging problem.

[0004] Chinese Patent Application CN109868526A discloses a method for preparing yttrium zirconate nanofibers from a zirconium-yttrium polymer precursor. Acetylacetone and triethylamine are reacted, and then triethylamine salt is removed with acetone to obtain a spinnable zirconium-yttrium acetylacetone polymer precursor. This method has expensive raw materials, complicated steps, and the application of acetone makes the preparation process have certain risks. Moreover, the fiber diameter prepared by this method is 500 nm, the grain growth rate is relatively fast, the anti-sintering performance is poor, and the fiber flexibility is also poor. Summary of the Invention

[0005] Aiming at the deficiencies of zirconate fiber materials in the prior art, such as low anti-sintering performance, poor flexibility, and complex preparation processes, the first object of the present invention is to provide an ultra-fine high-entropy zirconate-silica flexible fiber membrane. Through the high-entropy modification and crystal phase adjustment of zirconate, and the introduction of silica into high-entropy zirconate fibers, a flexible fiber membrane material with amorphous silica-coated ultra-fine high-entropy rare-earth zirconate nanoparticles is obtained, and an RE / Zr-O-Si amorphous interface is formed, so that the zirconate fibers of the present invention have better anti-sintering performance and flexibility, and can be used as structural reinforcement materials, high-temperature refractory materials, fire insulation materials, chemical corrosion-resistant materials, and catalyst carriers.

[0006] The second object of the present invention is to provide a preparation method for the ultra-fine high-entropy zirconate-silica flexible fiber membrane. The present invention adopts a simple electrospinning-calcination method, which can synthesize an ultra-fine high-entropy zirconate-silica flexible fiber membrane with uniform composition, high oxide content, and nanoscale at low temperature.

[0007] To achieve the above technical object, the present invention provides an ultra-fine high-entropy zirconate-silica flexible fiber membrane with the chemical formula RE2Zr2O7-SiO2, which is composed of amorphous silica-coated high-entropy rare-earth zirconate nanoparticles and has an RE / Zr-O-Si amorphous interface; the RE is composed of five rare-earth metal elements.

[0008] The key to the technical solution of the present invention lies in the high-entropy structural design of rare earth zirconate, which makes up for the deficiencies of single rare earth zirconate in terms of low toughness, heat insulation, and anti-sintering properties. Specifically, in the present invention, amorphous silica with high damage tolerance is introduced into the high-entropy rare earth zirconate fiber to obtain a fiber morphology in which amorphous silica wraps ultrafine high-entropy zirconate nanoparticles. This wrapping structure plays an important role in improving the performance of the fiber material of the present invention. Through this wrapping structure, a larger crystal phase-amorphous interface area can be caused, which can effectively hinder the grain growth and phase transformation of high-entropy rare earth zirconate. At the same time, in the present invention, through the A-site high-entropy design of the zirconate material, the high-entropy rare earth zirconate grains can simultaneously have a fluorite phase and a pyrochlore phase, which greatly ensures the high-temperature performance and anti-sintering performance of the material. The introduction of glassy SiO2 will lead to the formation of RE / Zr-O-Si bonds, which can further increase the crystallization temperature of the high-entropy zirconate particles and play a role in refining the high-entropy zirconate grains. Moreover, the heterogeneous interface between amorphous SiO2 and crystalline high-entropy zirconate can further significantly improve the high-temperature stability and anti-sintering performance of the material. In addition, this wrapped amorphous silica, as a soft interface, can buffer the stress generated inside the high-entropy zirconate through local plastic deformation and viscoelastic energy dissipation; the formation of RE / Zr-O-Si will also form a strong bonding interface between amorphous silica and high-entropy rare earth zirconate, which effectively improves the flexibility of the high-entropy zirconate fiber membrane.

[0009] As a preferred solution, the chemical formula is (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2. When high-entropy alloy design is carried out using La, Sm, Gd, Dy, Yb, and Zr, the material has better anti-sintering performance and toughness. This is mainly because the selected rare earth elements simultaneously include light rare earths (La, Sm, and Gd) and heavy rare earths (Dy and Yb), and their size disorder degree is as high as 8.911, which is easy to form a two-phase structure. Through the high-entropy effect, lattice distortion effect, retarded diffusion effect, and "cocktail" effect of the high-entropy material, a large number of grain boundaries and heterogeneous interfaces are contained in the fibers prepared by the present invention, and these grain boundaries and heterogeneous interfaces can cooperate with the RE / Zr-O-Si amorphous surface to further significantly improve the high-temperature stability and anti-sintering performance of the material.

[0010] As a preferred solution, the grain size of the high-entropy rare earth zirconate nanoparticles is 5-10 nm. The high-entropy rare earth zirconate nanoparticles of the present invention have obvious advantages in grain size after introducing silica to form a coated state. Fine nanocrystals have a higher specific surface area, and a high-density grain boundary can effectively improve the strength and toughness of the material.

[0011] As a preferred embodiment, the molar ratio of La, Sm, Gd, Dy, Yb and Zr is 1:1:1:1:1:5.

[0012] As a preferred embodiment, the diameter of the ultrafine high-entropy zirconate-silica flexible fiber membrane is 100-300 nm. This indicates that the precursor spinning solution prepared in the present invention has good spinnability. The small fiber diameter can improve the breaking strength and flexibility of the fiber, and the fine fibers are more likely to form a dense and disordered stacking structure, reducing the thermal conductivity of the fiber.

[0013] The present invention also provides a method for preparing an ultrafine high-entropy zirconate-silica flexible fiber membrane, which comprises the following steps:

[0014] (1) Weigh five rare earth metal salts and Zr salt according to the designed ratio, mix them and dissolve them with an organic solvent, and then add a spinning aid to obtain a RE-Zr precursor spinning solution;

[0015] (2) Add a silicon source and water to the RE-Zr precursor spinning solution to hydrolyze the silicon source and obtain a RE-Zr-Si precursor spinning solution;

[0016] (3) Electrospinning the RE-Zr-Si precursor spinning solution to obtain precursor fibers;

[0017] (4) Heat-treat the precursor fibers in an oxygen-containing atmosphere to obtain the product.

[0018] In the process of preparing the RE-Zr-Si precursor spinning solution in the present invention, no complex reaction is experienced, and the uniform mixing of alloy elements and Si elements at the atomic and molecular levels is directly achieved. The high-entropy zirconate-silica fibers prepared have a more uniform composition, and the electrospinning technology and heat treatment process further promote the formation of amorphous interfaces and coating morphologies.

[0019] Experiments have found that if the silicon source, water and metal salts are directly added synchronously, excessive hydrolysis of the silicon source will occur during long-term stirring, which is prone to gelation, so that the alloy elements and Si elements cannot achieve uniform mixing at the atomic level, and fiber breakage is likely to occur during the subsequent spinning process.

[0020] As a preferred embodiment, the organic solvent is at least one of anhydrous methanol, anhydrous ethanol, acetone and N, N-dimethylformamide (DMF); more preferably DMF. The selected organic solvent in the present invention can fully dissolve and mix the rare earth metal salts.

[0021] As a preferred solution, the spinning aid is at least one of polyethylene oxide and polyvinylpyrrolidone; polyethylene oxide has a higher viscosity than polyvinylpyrrolidone, which easily causes nozzle blockage and is not conducive to spinning. Moreover, polyvinylpyrrolidone is easily soluble in various solvents, and the solution preparation is more flexible. Therefore, the present invention further preferably uses polyvinylpyrrolidone.

[0022] As a preferred solution, the Zr salt is ZrOCl2 and its hydrates. The zirconium salt raw material used in the present invention is easily available and can be uniformly mixed with the five rare earth metal salts in an organic solvent, greatly simplifying the process steps.

[0023] As a preferred solution, the silicon source is at least one of tetraethyl orthosilicate, methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, and γ-chloropropyltriethoxysilane.

[0024] As a preferred solution, the mass ratio of the total mass of the five rare earth metal salts and the Zr salt to the mass of the organic solvent is 1:(1.6 - 3.3); within the solvent range selected in the present invention, the five rare earth metal salts and the Zr salt can be fully dissolved, facilitating the subsequent spinning process.

[0025] As a preferred solution, the addition amount of the silicon source is such that the molar ratio of Si to Zr is (0.05 - 0.4):1; and the mass ratio of water to the silicon source is (0.5 - 2):1. In the present invention, if the Si content is too low, the fiber flexibility is poor, while if the Si content is too high, silicate is easily formed, resulting in a lower fiber strength.

[0026] As a preferred solution, the content of the spinning aid is 5 - 11% of the total mass of the five rare earth metal salts, the Zr salt, and the organic solvent.

[0027] As a preferred solution, in step (1), after adding the spinning aid, it is necessary to stir and age for 24 - 72 h. The stirring process can ensure the full mixing of the rare earth salt and the zirconium salt and the full dissolution of the spinning aid, avoiding the generation of slag balls during the spinning process.

[0028] As a preferred embodiment, the parameters of the electrospinning are as follows: relative humidity is 30-60%, temperature is 25-45 °C, spinning voltage is 12-18 KV, receiving distance is 10-20 cm, and the advancing speed is 0.3-0.7 ml / h; the receiving device is a metal drum with a rotation speed of 100-500 r / min. The precursor fibers prepared under the electrospinning parameters of the present invention have the characteristics of uniform diameter, good continuity, and good flexibility. Moreover, the advancing speed of the spinning solution of the present invention has an important influence on the uniformity of the fibers. When the advancing speed is too fast, beaded precursor fibers are easily formed, and the fiber diameter and composition are uneven, resulting in the inability to effectively form the morphological structure of amorphous silica-coated high-entropy rare earth zirconate nanoparticles during the subsequent heat treatment process.

[0029] As a preferred embodiment, the heating program of the heat treatment is as follows: heating from room temperature to 1000-1200 °C at a rate of 1-5 °C / min, holding for 120-300 min; then cooling to 400-500 °C at a rate of 2-3 °C / min, and then cooling with the furnace. The linear heating of the present invention is beneficial to the formation of a uniform morphology, while the slow heating rate and a certain holding time are beneficial to the full bonding of RE / Zr-O-Si, ultimately forming the morphological characteristics of silica-coated high-entropy zirconate particles.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention firstly provides a preparation scheme for a high-entropy zirconate-silica flexible fiber membrane. The prepared high-entropy zirconate-silica fibers have a small diameter and controllable diameter, good continuity, foldability, and excellent flexibility.

[0032] (2) The process for preparing a spinnable rare earth-zirconium-silicon precursor spinning solution in the present invention is simple, and the precursor has stable properties and can be stored for a long time.

[0033] (3) The high-entropy zirconate-silica fiber membrane prepared in the present invention has uniform composition, extremely high purity, small and uniform diameter, dense structure, and the grain size of high-entropy zirconate is within 10 nm at high temperature, having good anti-sintering performance.

[0034] (4) The present invention does not require a complex heat treatment process or atmosphere protection, and the preparation process is simple and easy for batch production.

[0035] (5) By subjecting zirconate to high-entropy modification and adjusting the crystal phase, and introducing silica into the high-entropy zirconate fiber at the same time, a flexible fiber membrane material with amorphous silica-coated ultrafine high-entropy rare-earth zirconate nanoparticles is obtained, and an RE / Zr-O-Si amorphous interface is formed, enabling the zirconate fiber of the present invention to have better anti-sintering performance and flexibility, and can be used as a structural reinforcement material, a high-temperature refractory material, a fire-fighting heat-insulating material, a chemical corrosion-resistant material, and a catalyst support. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a process flow chart for preparing the high-entropy zirconate-silica fiber membrane of the present invention.

[0037] Figure 2 is the XRD pattern of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2 fiber membrane prepared in Example 1.

[0038] Figure 3 is the optical photograph of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2 precursor fiber membrane prepared in Example 1.

[0039] Figure 4 is the folding diagram of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2 fiber membrane prepared in Example 1.

[0040] Figure 5 is the low-magnification SEM image ( 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2 fiber membrane fiber prepared in Example 1 ( Figure 5 (a)) and the high-magnification SEM image ( Figure 5 (b)).

[0041] Figure 6 is the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2) TEM images of 2Zr2O7 - SiO2 fibers ( Figure 6 (a)), local enlarged images ( Figure 6 (b)), HADDF images ( Figure 6 (c)), elemental distribution maps of La ( Figure 6 (d)), elemental distribution maps of Sm ( Figure 6 (e)), elemental distribution maps of Gd ( Figure 6 (f)), elemental distribution maps of Dy ( Figure 6 (g)), elemental distribution maps of Yb ( Figure 6 (h)), elemental distribution maps of Zr ( Figure 6 (i)), elemental distribution maps of Si ( Figure 6 (j)) and elemental distribution maps of O ( Figure 6 (k)).

[0042] Figure 7 (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2Zr2O7 - SiO2 fibers prepared in Example 1 ( Figure 7 (a)) and (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2Zr2O7 fibers prepared in Comparative Example 2 ( Figure 7 (b)) in terms of heat insulation performance.

[0043] Figure 8 (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2Zr2O7 - SiO2 fibers prepared in Example 1 in terms of high - temperature stability. Specific Embodiments

[0044] To further illustrate the present invention, the following describes the content of the present invention in detail with reference to embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. It is only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments either.

[0045] Example 1

[0046] (1) Weigh equal molar amounts of five rare earth nitrate particles of La(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, Dy(NO3)3·6H2O, and Yb(NO3)3·5H2O and mix them evenly, denoted as D. RE ;

[0047] (2) Weigh the corresponding amount of ZrOCl2·8H2O according to the molar ratio of RE:Zr being 1:1, and mix it with D. RE Mix thoroughly and denote as D. RE-Zr .

[0048] (3) According to the mass ratio of the mixed salt D RE-Zr to the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), and dissolve the mixed salt D RE-Zr in DMF, and stir for 5 h until D RE-Zr is fully dissolved, denoted as S. RE-Zr .

[0049] (4) According to the content of the spinning aid being 7% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to the S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1.

[0050] (5) According to the molar ratio of silicon to zirconium being 0.25:1, and in accordance with the mass ratio of water to the silicon source being 1:1, weigh tetraethyl orthosilicate and water and add them to A1, and stir thoroughly for 8 h to ensure the full hydrolysis of tetraethyl orthosilicate to obtain the RE-Zr-Si precursor spinning solution A.

[0051] (6) Electrospinning of the precursor spinning solution A in step 5 is carried out under the electrospinning conditions of a temperature of 35 °C, a relative humidity of 40%, a rotation speed of the drum receiving device of 250 r / min, a spinning voltage of 16 KV, a receiving distance of 15 cm, and a feeding speed of 0.35 ml / h to obtain the precursor fiber membrane B. The prepared precursor fibers have the characteristics of uniform fiber diameter, good fiber continuity, and dense structure, as Figure 3 shown, with a diameter of 100 - 300 nm.

[0052] (7) Heat-treat the precursor fiber membrane B spun in step 6 in an air atmosphere at 1100 °C for 2 h to obtain the high-entropy zirconate-silica fiber. The fiber structure is dense, the fiber diameter is small, the zirconate particle size is within 10 nm, and it has good anti-sintering performance. The heat treatment procedure is as follows: heat from room temperature to 1100 °C at a heating rate of 5 °C / min, then hold for 2 h, and then cool to 500 °C at a cooling rate of 2 °C / min, and then cool to room temperature with the furnace.

[0053] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2 fibers have good heat insulation performance and flexibility. The heat insulation performance of the fibers with a thickness of 8 mm was tested with a butane flame (1380 °C). After heat treatment for 300 s, the back temperature was only 224 °C. The grain size of the high-entropy zirconate was 5-10 nm. After heat treatment at 1100 °C for 10 h, the grain size increased slightly to 30-50 nm, indicating that the prepared fibers have good anti-sintering performance. In addition, the fibers also have good high-temperature phase stability and still maintain the fluorite and pyrochlore biphasic structure after heat treatment at 1200 °C for 10 h. And it is shown by Figure 3 and Figure 4 that the fibers have good flexibility and can be bent and folded. It can be clearly seen from Figure 6 that the high-entropy rare-earth zirconate nanoparticles are wrapped by amorphous silica and have a RE / Zr-O-Si amorphous interface.

[0054] Example 2

[0055] (1) Weigh 5 kinds of rare-earth nitrate particles of equimolar amounts of La(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, Dy(NO3)3·6H2O, and Yb(NO3)3·5H2O and mix them evenly, denoted as D RE ;

[0056] (2) Weigh the corresponding amount of ZrOCl2·8H2O according to the molar ratio of RE:Zr of 1:1, and mix it well with D RE and denote it as D RE-Zr .

[0057] (3) According to the mass ratio of the mixed salt D RE-Zr to the solvent of 1:2, weigh the corresponding amount of N,N-dimethylformamide (DMF), dissolve the mixed salt D RE-Zr in DMF, and stir for 5 h until D RE-Zr is fully dissolved, denoted as S RE-Zr .

[0058] (4) According to the content of the spinning aid being 5% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to the S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1.

[0059] (5) According to the molar ratio of silicon to zirconium being 0.25:1, and in accordance with the mass ratio of water to silicon source being 1:1, weigh tetraethyl orthosilicate and water and add them to A1, stir well for 8 h to ensure that tetraethyl orthosilicate is fully hydrolyzed, and obtain the RE-Zr-Si precursor spinning solution A.

[0060] (6) Carry out electrospinning on the precursor spinning solution A in step 5 under the electrospinning conditions of a temperature of 30 °C, a relative humidity of 40%, a rotational speed of the drum receiving device of 250 r / min, a spinning voltage of 15.5 KV, a receiving distance of 15 cm, and a propulsion speed of 0.35 ml / h to obtain the precursor fiber B.

[0061] (7) Sinter the precursor fiber B spun in step 6 in an air atmosphere. The heat treatment procedure is as follows: heat from room temperature to 1000 °C at a heating rate of 5 °C / min, then hold for 2 h, then cool to 500 °C at a cooling rate of 2 °C / min, and then cool to room temperature with the furnace to obtain the nano-high-entropy zirconate fiber.

[0062] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2Zr2O7-SiO2 fiber has good heat insulation performance and flexibility. Test the heat insulation performance of the fiber with a thickness of 8 mm using a butane flame (1380 °C). After heat treatment for 300 s, its back temperature is 228 °C. The grain size of the high-entropy zirconate is 5 - 10 nm. After heat treatment at 1100 °C for 10 h, the grain size slightly increases to 20 - 50 nm, indicating that the prepared fiber has good anti-sintering performance. In addition, the fiber also has good high-temperature phase stability and still maintains the fluorite and pyrochlore double-phase structure after heat treatment at 1200 °C for 10 h.

[0063] Example 3

[0064] (1) Weigh 5 kinds of rare earth chloride particles of equimolar amounts of LaCl3·6H2O, SmCl3·6H2O, GdCl3·6H2O, DyCl3·6H2O, and YbCl3·6H2O and mix them evenly, denoted as D RE ;

[0065] (2) Weigh the corresponding amount of ZrOCl2·8H2O according to the molar ratio of RE:Zr being 1:1, and mix it fully with D RE and denote it as D RE-Zr .

[0066] (3) According to the mass ratio of the mixed salt D RE-Zr and the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), and mix the mixed salt D RE-ZrDissolve it in DMF and stir for 5 h until D RE-Zr is fully dissolved and denoted as S RE-Zr .

[0067] (4)According to the content of the spinning aid being S RE-Zr which is 7% of the solution mass, weigh out the corresponding amount of polyvinylpyrrolidone (PVP) and add it to S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1

[0068] (5)According to the molar ratio of silicon to zirconium being 0.1:1 and in accordance with the mass ratio of water to silicon source being 1.5:1, weigh out tetraethyl orthosilicate and water and add them to A1, and stir thoroughly for 5 h to ensure the full hydrolysis of tetraethyl orthosilicate to obtain the RE-Zr-Si precursor spinning solution A

[0069] (6)Carry out electrospinning on the precursor spinning solution A in step 5 under the electrospinning conditions of a temperature of 40 °C, a relative humidity of 40%, a rotational speed of the roller receiving device of 300 r / min, a spinning voltage of 16 KV, a receiving distance of 12 cm, and a propulsion speed of 0.5 ml / h to obtain the precursor fiber B

[0070] (7)Carry out heat treatment on the precursor fiber B spun in step 6 in an air atmosphere. The heat treatment procedure is: from room temperature to 1100 °C at a heating rate of 5 °C / min, then hold for 2 h, and then cool down to 500 °C at a cooling rate of 2 °C / min, and then cool to room temperature with the furnace to obtain the nano high-entropy zirconate fiber

[0071] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2 fiber has good heat insulation performance and flexibility. The heat insulation performance of the fiber with a thickness of 8 mm is tested with a butane flame (1380 °C). After heat treatment for 300 s, its back temperature is 242 °C. After heat treatment at 1100 °C for 10 h, the grain size slightly increases to 30 - 60 nm, which indicates that the prepared fiber has good anti-sintering performance. In addition, the fiber also has good high-temperature phase stability and still maintains the fluorite and pyrochlore biphasic structure after heat treatment at 1200 °C for 10 h

[0072] Example 4

[0073] (1)Weigh out equimolar amounts of 5 rare earth nitrate particles of La(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, Dy(NO3)3·6H2O, and Yb(NO3)3·5H2O and mix them evenly, denoted as DRE ;

[0074] (2) Weigh the corresponding amount of ZrOCl2·8H2O according to the molar ratio of RE:Zr being 1:1, and mix it with D RE thoroughly, and denote it as D RE-Zr .

[0075] (3) According to the mass ratio of the mixed salt D RE-Zr to the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), and dissolve the mixed salt D RE-Zr in DMF, and stir for 5 h until D RE-Zr is fully dissolved, and denote it as S RE-Zr .

[0076] (4) According to the content of the spinning aid being 7% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to the S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1.

[0077] (5) According to the molar ratio of silicon to zirconium being 0.4:1, and in accordance with the mass ratio of water to the silicon source being 1:1, weigh tetraethyl orthosilicate and water and add them to A1, and stir thoroughly for 5 h to ensure the full hydrolysis of tetraethyl orthosilicate, and obtain the RE-Zr-Si precursor spinning solution A.

[0078] (6) Electrospin the precursor spinning solution A in step 5 under the electrospinning conditions of a temperature of 35 °C, a relative humidity of 30%, a rotation speed of the drum receiving device of 250 r / min, a spinning voltage of 18 KV, a receiving distance of 15 cm, and a propulsion speed of 0.35 ml / h to obtain the precursor fiber B.

[0079] (7) Heat-treat the precursor fiber B spun in step 6 in an air atmosphere. The heat-treatment program is: heat from room temperature to 1200 °C at a heating rate of 5 °C / min, then hold for 2 h, and then cool at a cooling rate of 2 °C / min to 500 °C, and then cool with the furnace to room temperature to obtain the nano high-entropy zirconate fiber.

[0080] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2)The 2Zr2O7-SiO2 fibers have good heat insulation performance and flexibility. The heat insulation performance of the fibers with a thickness of 8 mm was tested using a butane flame (1380 °C), and the back temperature was only 235 °C after 300 s of heat treatment. After heat treatment at 1100 °C for 10 h, the grain size increased slightly to 40 - 70 nm, indicating that the prepared fibers have good anti-sintering performance. In addition, the fibers also have good high-temperature phase stability and still maintain the fluorite and pyrochlore double-phase structure after heat treatment at 1200 °C for 10 h.

[0081] Comparative Example 1

[0082] (1)According to the molar ratio of Yb:Zr being 1:1, the corresponding amounts of Yb(NO3)3·5H2O and ZrOCl2·8H2O raw materials were weighed and fully mixed, denoted as D Yb-Zr .

[0083] (2)According to the mass ratio of the mixed salt D Yb-Zr and the solvent being 1:2.7, the corresponding amount of N,N-dimethylformamide (DMF) was weighed, and the mixed salt D Yb-Zr was dissolved in DMF and stirred for 5 h until D Yb-Zr was fully dissolved, denoted as S Yb-Zr .

[0084] (3)According to the content of the spinning aid being 7% of the mass of the S Yb-Zr solution, the corresponding amount of polyvinylpyrrolidone (PVP) was weighed and added to the S RE-Zr solution and stirred until fully dissolved. The stirring and aging time was 48 h to obtain the Yb-Zr precursor spinning solution, denoted as A1.

[0085] (4)According to the molar ratio of silicon to zirconium being 0.25:1 and the mass ratio of water to the silicon source being 1:1, tetraethyl orthosilicate and water were weighed and added to A1, and stirred thoroughly for 8 h to ensure the full hydrolysis of tetraethyl orthosilicate, obtaining the Yb-Zr-Si precursor spinning solution A.

[0086] (5)The precursor spinning solution A in step 4 was electrospun under the spinning conditions of a temperature of 35 °C, a relative humidity of 40%, a rotational speed of the drum receiving device of 250 r / min, a spinning voltage of 16 KV, a receiving distance of 15 cm, and a feeding speed of 0.35 ml / h to obtain the precursor fiber B.

[0087] (6)The precursor fiber B spun in step 5 was heat-treated at 1100 °C for 2 h in an air atmosphere to obtain ytterbium zirconate-silica fibers. The heat treatment procedure was as follows: heating from room temperature to 1100 °C at a heating rate of 5 °C / min, then holding for 2 h, and then cooling to 500 °C at a cooling rate of 2 °C / min, and then furnace cooling to room temperature.

[0088] Compared with Example 1, the ytterbium zirconate-silica fiber structure is relatively dense, but the ytterbium zirconate particle size is relatively large, 20-40 nm, the anti-sintering performance is poor, and the grain size rapidly increases to 150-200 nm after heat treatment at 1100 °C for 10 h, and the flexibility of the fiber membrane is poor.

[0089] Comparative Example 2

[0090] Steps 1-4 and steps 6-7 of this comparative example are the same as those of Example 1, and the only difference lies in the following steps:

[0091] (5) According to the molar ratio of silicon to zirconium being 0:1, no silicon source was introduced into the RE-Zr precursor spinning solution.

[0092] Compared with Example 1, the obtained high-entropy zirconate fiber has poor flexibility, and the size of the high-entropy zirconate grains is relatively large, within 20 nm. After heat treatment at 1100 °C for 10 h, the grain size increases to 50-80 nm. Compared with Example 1, the anti-sintering performance decreases. In addition, the heat insulation performance also decreases. The heat insulation performance of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7 fiber with a thickness of 8 mm was tested by a butane flame, and the back temperature was 259 °C.

[0093] Comparative Example 3

[0094] Steps 1-5 and step 7 of this comparative example are the same as those of Example 1, and the only difference lies in the following steps:

[0095] (6) The precursor spinning solution A in step 5 was electrospun under the electrospinning conditions of a temperature of 35 °C, a relative humidity of 40%, a rotation speed of the drum receiving device of 250 r / min, a spinning voltage of 16 KV, a receiving distance of 15 cm, and a propulsion speed of 1 ml / h to obtain a precursor fiber membrane B.

[0096] Compared with Example 1, the propulsion speed of the spinning solution is too fast, the diameter of the prepared nanofibers increases, about 400 nm, and beaded fibers appear, making it difficult to form fibers with a uniform diameter.

[0097] Comparative Example 4

[0098] Steps 1-2 and steps 5-7 of this comparative example are the same as those of Example 1, and the only difference lies in the following steps:

[0099] (3) According to the mass ratio of the mixed salt D RE-Zr and the solvent being 1:2.7, the corresponding amount of N,N-dimethylformamide (DMF) was weighed, and the mixed salt D RE-Zr was dissolved in DMF and stirred for 0.5 h until D RE-ZrDissolve, denoted as S RE-Zr .

[0100] (4) According to the content of the spinning aid being S RE-Zr which is 7% of the solution mass, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 6 h to obtain a precursor spinning solution.

[0101] Compared with Example 1, the aging time of the precursor spinning solution was changed. The mixed salts were difficult to dissolve and mix evenly, and the spinning aid could not be fully dissolved. The viscosity of the spinning solution was low and the spinnability was poor. There were a large number of slag balls during the electrospinning process, and the fibers were short and had low strength.

Claims

1. An ultrafine high-entropy zirconate-silica flexible fiber membrane, characterized in that: The chemical formula is (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2Zr2O7 - SiO2, which is composed of amorphous silica - coated high - entropy rare - earth zirconate nanoparticles and has an RE / Zr - O - Si amorphous interface; the RE is composed of La, Sm, Gd, Dy, and Yb; The high-entropy rare-earth zirconate nanoparticles have a fluorite and pyrochlore dual-phase structure; The preparation of the ultrafine high-entropy zirconate-silica flexible fiber membrane includes the following steps: (1) Weigh five rare-earth metal salts and Zr salt according to the designed ratio, mix them, dissolve them with an organic solvent, and then add a spinning aid to obtain a RE-Zr precursor spinning solution; (2) Add a silicon source and water to the RE-Zr precursor spinning solution to hydrolyze the silicon source and obtain a RE-Zr-Si precursor spinning solution; (3) Electrospun the RE-Zr-Si precursor spinning solution to obtain precursor fibers; (4) Heat-treat the precursor fibers in an oxygen-containing atmosphere to obtain the product.

2. The ultra-fine high-entropy zirconate-silica flexible fiber membrane according to claim 1, characterized in that: The grain size of the high-entropy rare-earth zirconate nanoparticles is 5-10 nm.

3. The superfine high-entropy zirconate-silica flexible fiber membrane according to claim 2, wherein: The molar ratio of La, Sm, Gd, Dy, Yb and Zr is 1:1:1:1:1:

5.

4. A method for preparing an ultrafine high-entropy zirconate-silica flexible fiber membrane according to any one of claims 1 to 3, characterized in that: It includes the following steps: (1) Weigh five rare-earth metal salts and Zr salt according to the designed ratio, mix them, dissolve them with an organic solvent, and then add a spinning aid to obtain a RE-Zr precursor spinning solution; (2) Add a silicon source and water to the RE-Zr precursor spinning solution to hydrolyze the silicon source and obtain a RE-Zr-Si precursor spinning solution; (3) Electrospun the RE-Zr-Si precursor spinning solution to obtain precursor fibers; (4) Heat-treat the precursor fibers in an oxygen-containing atmosphere to obtain the product.

5. The preparation method of an ultrafine high-entropy zirconate-silica flexible fiber membrane according to claim 4, wherein: The organic solvent is at least one of anhydrous methanol, anhydrous ethanol, acetone and N, N-dimethylformamide; The spinning aid is at least one of polyethylene oxide and polyvinylpyrrolidone; The Zr salt is ZrOCl2 and its hydrates; The silicon source is at least one of tetraethyl orthosilicate, methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane and γ-chloropropyltriethoxysilane.

6. The preparation method of an ultrafine high-entropy zirconate-silica flexible fiber membrane according to claim 5, wherein: The mass ratio of the total mass of the five rare-earth metal salts and Zr salt to the mass of the organic solvent is 1:(1.6-3.3); The addition amount of the silicon source is based on the molar ratio of Si to Zr of (0.05-0.4):1; and the mass ratio of water to the silicon source is (0.5-2):

1.

7. The preparation method of an ultra-fine high-entropy zirconate-silica flexible fiber membrane according to claim 4, characterized in that: In step (1), after adding the spinning aid, it needs to be stirred and aged for 24-72 h.

8. The preparation method of an ultrafine high-entropy zirconate-silica flexible fiber membrane according to claim 7, characterized in that: The parameters of the electrospinning are: relative humidity is 30-60%, temperature is 25-45 °C, spinning voltage is 12-18 KV, receiving distance is 10-20 cm, and the advancing speed is 0.3-0.7 ml / h; the receiving device is a metal roller with a rotation speed of 100-500 r / min.

9. The preparation method of an ultrafine high-entropy zirconate-silica flexible fiber membrane according to claim 7 or 8, characterized in that: The heating-up program of the heat treatment is: heating from room temperature to 1000-1200 °C at a rate of 1-5 °C / min, holding for 120-300 min; then cooling to 400-500 °C at a rate of 2-3 °C / min, and then cooling with the furnace.

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